1. Field of the Invention
The invention relates to a method for making a cable with conductive bumps arranged in an array and a method for connecting the cable to an electronic component, more particularly, the cable can electrically connect to the electronic component without need for an anisotropic-conductive paste or film (ACP or ACF).
2. Related Art
Anisotropic-conductive paste (ACP) or anisotropic-conductive film (ACF) has been commonly applied as a major compound for connecting a cable to an integrated circuit (IC) or attaching a circuit board to an LCD glass substrate. The major ingredient of the ACP or ACF comprises a great quantity of small conductive particles contained in glue.
When electrically connecting the LCD glass substrate to the circuit board by the ACP or ACF through a pressing process, the conductive particles will be distributed between the substrate and the circuit board. For regions where these particles have been pressed, the particles serve as conductive material between the substrate and the circuit board. On the contrary, for regions where the particles have not been pressed, electrical signals can not be transmitted between the substrate and the circuit board even though they are joined together by the glue.
For example, with reference to FIGS. 6A and 6B, a cable (70) has multiple conductive circuits (71) that are electrically connected to substrate terminals (not numbered) on a substrate (72) by ACP/ACF (80). The ACP/ACF (80) that contains the conductive particles (81) is distributed between the cable (70) and the substrate (72). The substrate (72) can be an LCD glass substrate, a printed circuit board etc. For an LCD glass substrate, the substrate terminals can be formed by indium tin oxide (ITO) or metal wires.
With reference to FIG. 7, the ACP/ACF (80) is applied to join terminals (74) of an integrated circuit (IC)(73) to the circuits (71) of the cable (70). The particles (81) that have been pressed in the ACP/ACF (80) also serve as material to make an electrical connection between the terminals (74) and the circuits (71).
With reference to FIG. 8, in another embodiment of prior art, non-conductive film or paste (NCF or NCP) (82) is applied to join the IC (73) and the cable (70) together. The terminals (74) of the IC directly contact the circuits (71) of the cable (70). The disadvantage raised in this prior art is the unsatisfactory reliability of connection between the IC (73) and the cable (70). If the circuits (71) mis-align with the terminals (74), a defective electrical connection may possibly exist between cable (70) and the IC (73) because no conductive particles are contained in the NCF/NCP (82).
Although using the ACP/ACF (80) can solve the drawback of the device in FIG. 8, the ACP/ACF (80) still causes other problems.
1. Specific space is required where the glue of ACP/ACF can flow between the cable and the substrate or IC. However, the conductive particles may thus be unequally distributed due to the flowing motions of the glue. The connecting reliability is then reduced.
2. The width and length of the conductive circuits must be carefully determined upon the sizes of the particles, otherwise an undesired short circuit or a failed electrical connection between the cable and the task object accordingly occur.
3. The fabricating processes of the ACP/ACF are complex.
4. The cost of the ACP/ACF is quite high since only a particular material is suitable for manufacture of the conductive particles.
For the above reasons, a novel cable is proposed to overcome the shortcoming of the prior arts using the ACP/ACF.